The present invention relates to a hand tool, such as a wrench, having a self-securing handle. The present invention, in particular, relates to a tool having a separately formed handle which is assembled over and self-secured to the tool without additional fasteners or adhesives.
Recently, many tool manufacturers have added ergonomic or coated handles atop metal tools, such as wrenches, to improve the grip and tactile feel of the tool during use. Normally, the metal tool is inserted in a mold and one or more layers of a handle material are molded around the shaft of the tool. For example, U.S. Pat. No. 5,740,586 describes a technique of coating tool shafts with multiple layers of elastomeric materials by injection over-molding.
One problem with the known manufacturing techniques is flashing. The molds used in the over-molding process are precise, and the tool must fit precisely therein. It is difficult to mass produce tools, especially by forging, with the necessary degree of precision such that each tool will precisely fit into the mold. Because the molds will not accept varying shapes of forged tools, even minor variations in the cross-section of a tool can prevent sufficient mold contact, and coating materials are expelled from the mold at the open end through which the non-coated portion of the tool extends, and along any nonconforming portion of the tool shaft. This makes it nearly impossible to use a single mold to manufacture multiple forged tool handles without the presence of flashing that must be subsequently removed.
It is generally known to use inserts to compensate for tool variations and essentially plug the gaps that would allow flashing. These inserts, however, also need to be precisely manufactured to correct individual nonconforming fits, of which there may be a number of variations. This technique is not a desirable solution to the problem, because it adds an additional step in the manufacturing process and increases the overall production cost of the tool.
Even if the handle is molded apart from the tool shaft to avoid the flashing problem, another manufacturing step, such as riveting or applying an adhesive, is required to secure the handle firmly onto the tool shaft.
It would be desirable to provide a tool having a self-securing handle than can be formed separately from the tool and attached thereto in a single assembly step that does not necessitate using rivets, adhesives, and the like. This would eliminate the problems commonly experienced with over-molding handle material, decrease manufacturing costs, and increase the efficiency of the overall manufacturing process.
It is an object of the invention to overcome the drawbacks of the prior art, particularly to provide a separate, self-securing handle for a tool which is assembled over the tool in a single assembly step.
In accordance with one embodiment of the present invention, a self-securing handle for a tool having a longitudinally extending main body portion is provided. The self-securing handle includes an elongate body having a first end and a second end, and includes a central cavity passing therethrough from the first end to the second end. The self-securing handle further includes a securing mechanism located within the elongate body proximate the second end. The self-securing handle receives the tool main body portion within the central cavity, and the securing mechanism mates with a receiving structure on the tool main body portion to secure the handle to the tool main body portion.
In accordance with a preferred embodiment, the self-securing handle further includes an inner core body having a first end proximate the first end of the handle, and a second end proximate the second end of the handle. The inner core body includes an inner surface which opposes the main body portion of the tool and an outer surface, and extends longitudinally from the first end toward the second end thereof. Further, the central cavity of the handle passes through the inner core body from the first end to the second end thereof. The self-securing handle also includes an external layer extending longitudinally from the first end of the handle toward the second end, and the external layer substantially covers an outer surface of the inner core body.
It is preferred that the inner core body is made of a hard grade elastomer material, more preferably a polypropylene material. It is also preferred that the external layer is made of a flexible grade elastomeric material, more preferably SANTOPRENE (a flexible elastomeric material).
In accordance with another preferred embodiment, the securing mechanism includes at least one, but more preferably two, securing tabs positioned within the central cavity on opposite sides thereof. The securing tabs extend radially into the central cavity and axially toward the second end of the handle. A stop member is also provided, positioned proximate the first end of the elongate body and located within the central cavity of the elongate body, for preventing axial movement of the handle along the main body portion of the tool in a direction toward the first end of the handle.
According to another embodiment of the present invention, a tool is provided including a tool head portion, and a tool main body portion having a first end and an opposed second end. The first end is connected to the tool head portion, and the tool main body portion extends longitudinally from the first end toward the second end. The tool main body portion further includes a receiving structure adjacent the second end thereof. A self-securing handle is also provided, including an elongate body having a first end and a second end, and having a central cavity passing therethrough from the first end to the second end, such that the tool main body is positioned within the central cavity. The self-securing handle further includes a securing mechanism within the elongate body proximate the second end, which mates with the receiving structure of the tool main body portion for securing the handle to the tool main body portion.
It is preferred that the cross-sectional shape of the tool main body portion substantially corresponds to the cross-sectional shape of the central cavity, and the crosssectional shape is substantially non-circular to prevent rotation of the handle about the longitudinal axis of the tool main body portion. It is also preferred that the tool includes a stepped portion on an outer surface of the tool main body portion and a corresponding stepped portion on an inner surface of the central cavity. These stepped portions prevent the handle, once in the locked position, from moving toward the first end of the tool main body portion.
According to another embodiment of the present invention, a method for assembling a self-securing handle on a tool is provided, and includes: providing a tool having a head portion and a longitudinally extending main body portion, the main body portion having a first end proximate the tool head portion, an opposing second end, and a receiving structure adjacent the second end; providing a self-securing handle including an elongate body having a first end and a second end, the elongate body having a central cavity passing therethrough from the first end to the second end, and a securing mechanism proximate the second end thereof; and inserting the tool main body portion into the first end of the self-securing handle so that the securing mechanism mates with the receiving structure to secure the handle to the tool main body portion.
According to a preferred method of the present invention, a stopping member is provided proximate the first end of the tool main body portion for preventing axial movement of the handle along the tool main body portion in a direction toward the first end of the handle. More preferably, a stepped portion on an outer surface of the tool main body portion and a corresponding stepped portion on an inner surface of the central cavity define the stopping member.